Photon Fluence Rate and Temperature Effects on Temperate Atlantic Kelp Species

The Portuguese coast forms a key biogeographic transition zone where co-occurring kelp species show limited vertical overlap. This study aimed to understand whether temperature and light responses help explain the vertical niche differentiation of <i>Laminaria ochroleuca</i>, <i>Sa...

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Bibliographic Details
Main Authors: Tomás F. Pinheiro, Silvia Chemello, Isabel Sousa-Pinto, Tânia R. Pereira
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Phycology
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Online Access:https://www.mdpi.com/2673-9410/5/2/27
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Summary:The Portuguese coast forms a key biogeographic transition zone where co-occurring kelp species show limited vertical overlap. This study aimed to understand whether temperature and light responses help explain the vertical niche differentiation of <i>Laminaria ochroleuca</i>, <i>Saccorhiza polyschides</i>, and <i>Phyllariopsis brevipes</i>. Results revealed that <i>P. brevipes</i>, despite occupying the southernmost range, showed a low thermal tolerance: 27 °C significantly increased respiration rates, indicating metabolic stress, and exposition at 30 °C caused physiological stress. In contrast, <i>L. ochroleuca</i> and <i>S. polyschides</i> exhibited a greater thermal resilience but displayed high light requirements, with evident stress at 30 °C. These results suggest that light availability may play a key role in shaping vertical zonation in a climate warming scenario, with species adapted to low light occupying deeper subtidal zones. <i>S. polyschides</i>, a high light-requiring species, dominates the shallow subtidal region, while <i>L. ochroleuca</i>, also high light-requiring and temperature-tolerant, is abundant in both intertidal pools and shallow subtidal habitats. These findings raise new hypotheses regarding future distribution patterns under climate change: while <i>L. ochroleuca</i> may continue expanding polewards and potentially replace other <i>Laminaria</i> spp. at shallow depths, low-light-adapted, cold-water species may retain a competitive advantage in deeper zones.
ISSN:2673-9410